CVE-2021-21411

Description


OAuth2-Proxy is an open source reverse proxy that provides authentication with Google, Github or other providers. The `--gitlab-group` flag for group-based authorization in the GitLab provider stopped working in the v7.0.0 release. Regardless of the flag settings, authorization wasn't restricted. Additionally, any authenticated users had whichever groups were set in `--gitlab-group` added to the new `X-Forwarded-Groups` header to the upstream application. While adding GitLab project based authorization support in #630, a bug was introduced where the user session's groups field was populated with the `--gitlab-group` config entries instead of pulling the individual user's group membership from the GitLab Userinfo endpoint. When the session groups where compared against the allowed groups for authorization, they matched improperly (since both lists were populated with the same data) so authorization was allowed. This impacts GitLab Provider users who relies on group membership for authorization restrictions. Any authenticated users in your GitLab environment can access your applications regardless of `--gitlab-group` membership restrictions. This is patched in v7.1.0. There is no workaround for the Group membership bug. But `--gitlab-project` can be set to use Project membership as the authorization checks instead of groups; it is not broken.

CvssV3 impact


BaseSeverity

MEDIUM

ConfidentialityImpact

LOW

AttackComplexity

LOW

Scope

CHANGED

AttackVector

NETWORK

AvailabilityImpact

NONE

IntegrityImpact

LOW

PrivilegesRequired

HIGH

BaseScore

5.5

VectorString

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N

Version

3.1

UserInteraction

NONE

CvssV2 impact


AccessComplexity

LOW

ConfidentialityImpact

PARTIAL

AvailabilityImpact

NONE

IntegrityImpact

PARTIAL

BaseScore

5.5

VectorString

AV:N/AC:L/Au:S/C:P/I:P/A:N

Version

2.0

AccessVector

NETWORK

Authentication

SINGLE